981
FXUS63 KGRR 010745
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
345 AM EDT Tue Jul 1 2025

.KEY MESSAGES...

- Spotty Chances for Showers/Storms Wednesday through Friday

- Cold Front to Bring Showers/Storms Saturday night into Sunday

- Near Normal Temperatures Today then Slow Warming Trend

&&

.DISCUSSION...
Issued at 345 AM EDT Tue Jul 1 2025

- Spotty Chances for Showers/Storms Wednesday through Friday

We look to be precipitation free today as drier air settles in on
westerly winds. On Wednesday however, during the afternoon and
evening, we may see some isolated/scattered shower and
thunderstorm activity. The forcing for the precipitation looks to
be via 1) a lake breeze boundary pushing into interior portions
of the Lower Peninsula as well as 2) a weak stationary boundary
sagging south out of Northern Lower. Precipitation coverage is not
expected to be widespread, but both the SREF and the HREF are
showing this potential (two trusted sources).

On Thursday the weak boundary is still in the vicinity and the
SREF once again is indicating some weak activity bubbling up
during the heat of the day. Again, not expecting widespread
precipitation and in fact most areas will likely remain dry.

Friday the models bring the heat and humidity back into the area
in full swing. As the moisture moves back in, it appears as though
we have some small chances for warm frontal showers and storms.

- Cold Front to Bring Showers/Storms Saturday night into Sunday

Better chance for showers and storms will come Saturday night into
Sunday as a cold front moves into the area from the north and
west. The models have slowed this front up by about 12 hours in
the latest runs. The front is being driven by a weak shortwave
trough in the mid levels which is losing amplitude as it moves in.
That said, it is the best forcing we see in the 7 day forecast.
Typical mid summer forecast this morning where there is very
little forcing throughout with conditions being dominated by weak
fronts and thermodynamics. Chances for rain mid week is only 20-30
pct. Chances Saturday night are 40-60 pct.

- Near Normal Temperatures Today then Slow Warming Trend

We will be less humid today and slightly cooler with highs back
into the lower 80s which is near normal. Ridging will build aloft
as we head into the end of the week. 850mb temperatures will rise
as well from around +13C today to +18 to +20C Friday into
Saturday. Highs will nudge up each day as we move forward with
lower 90s possible on Friday and likely Saturday.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 206 AM EDT Tue Jul 1 2025

A band of post frontal mid and high clouds remain above the TAF
sites at 06Z. These clouds will continue to peel off to the east
with the front and all of the TAF sites should be clear by around
12Z. Diurnal cumulus clouds are expected today with scattered to
possibly broken clouds developing after 15Z. These clouds will
clear during the evening hours. Bottom line...VFR weather is
expected throughout this TAF period. Winds today will be gusty
from the west-northwest (270-300) at 12-20 knots.

&&

.MARINE...
Issued at 345 AM EDT Tue Jul 1 2025

High resolution models continue to indicate winds remaining below
advisory levels for the next several days. Even though a cold
front moved through yesterday, the winds in the wake of the front
are fairly light. Winds will pick up some today, but remain
generally 15 knots or less over the lake. Surface ridging builds
in for Wednesday and Thursday bringing even lighter winds. It is
not until we get to Saturday when a stronger southwest flow
develops that we could see higher winds/larger waves. Waves will
be 2 feet or less through Friday, so good boating/swimming
conditions are anticipated.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

DISCUSSION...DUKE
AVIATION...DUKE
MARINE...DUKE